# Operators Reversing Orthogonality and Characterization of Inner Product Spaces

Document Type: Original Article

Author

Institute of Mathematics, Pedagogical University of Cracow, Podchorążych 2, 30-084 Kraków, Poland.

Abstract

In this short paper we answer a question posed by Chmieliński in [Adv. Oper. Theory, 1 (2016), no. 1, 8-14].
Namely, we prove that among normed spaces of dimension greater than two,
only inner product spaces admit nonzero linear operators which reverse the Birkhoff orthogonality.

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Main Subjects